Variable tension post fixation

ABSTRACT

A variable tension post fixation device includes an outer screw including a head configured to receive a driver, a conical tip, a threaded shaft extending between the head and the tip, and an incompletely cannulated core, and an inner screw including a proximal end, a distal end, and at least one suture hole, wherein the inner screw is configured to be insertably coupled with the outer screw.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application Ser. No. 61/104,881 filed on Oct. 13,2008, and incorporated herein by reference. This application is relatedto U.S. Non-Provisional patent application Ser. No. ______, filed oneven date herewith, having attorney docket number R615.103.102, andincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to a medical device thatfacilitates orthopaedic procedures requiring tensioning and fixation ofsutures to bone. With this device, variable tension may be appliedindependently to one or more different sets of sutures. For example,during anterior cruciate ligament (ACL) reconstruction, the device maybe used as primary or secondary fixation of an ACL graft on the tibialside of the reconstruction construct. With the device, variable tensionmay be applied independently to the sutures, such as those found withsingle or double bundle ACL reconstruction.

BACKGROUND OF THE INVENTION

Anterior cruciate ligament (ACL) reconstruction is one of the mostcommonly performed procedures on the human knee. Primary surgical goalsduring ACL reconstruction include restoring translational and rotationalstability of the knee. These goals are often achieved by utilizing asoft tissue graft that is fixated on the femoral and tibial sides of thejoint. A common cause of graft failure within the first 6 weeks is lossof fixation strength. This loss of fixation strength is more commonlyfound on the tibial side rather than the femoral attachment of the ACLgraft.

To alleviate the loss of fixation strength, surgeons often use a screwand washer on the tibial side of the joint to create a backup fixationwhereby the suture tails of the ACL graft are tied around the screw as apost. A simple limitation with this type of backup fixation, however, isthat the sutures tied around the screw can not be tensioned once theyare tied. Furthermore, with the advent of double bundle ACLreconstruction, a need for independent tensioning of each ACL bundle hasevolved. Unfortunately, the simple screw and washer configuration doesnot allow for independent tensioning of the four suture tails on the twoindependent bundle limbs.

The ability to attach sutures around a post and then be able to furthertension those sutures to a desired tension after they have been tiedwould be beneficial, for example, during ACL reconstruction. Also, adesirable device would allow for independent tensioning of two sets ofsuture tails on a single tibial post, including tensioning of suturetails often found on the tibial side of the joint when performing adouble bundle ACL graft.

For these and other reasons, there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a through 1 i illustrate an embodiment of a variable tensionpost fixation device.

FIGS. 2 a through 2 g illustrate an embodiment of a variable tensionpost fixation device.

FIGS. 3 a through 3 h illustrate an embodiment of a variable tensionpost fixation device.

FIGS. 4 a through 4 b illustrate an embodiment of a variable tensionpost fixation device.

FIG. 5 illustrates one technique of performing ACL reconstruction usinga variable tension post fixation device as described herein.

DETAILED DESCRIPTION

A desirable fixation device would provide orthopaedic surgeonsperforming single or double bundle ACL reconstruction with the abilityto tension suture tails after the suture tails are attached to thefixation device. The device would allow the surgeon to tension eachstrand of the suture tails to a desired tension, and then tension theentire construct one last time in a combined fashion if desired.

Techniques

With reference to FIG. 5, one technique of performing single or doublebundle ACL reconstruction is described. The tunnels are drilled, thegraft(s) are passed through their respective tunnels, and the femoralfixation is placed. In double bundle reconstruction, each bundle ispulled out of their respective tibial tunnel. For fixation of eachbundle, the surgeon may use interference screws in each tunnel as aprimary fixation. Secondary fixation may include variable tensioningwith separate fixation devices, as described herein, positioned distalto the exit of each tibial tunnel or may include combining the fourstrands of the sutures from the two bundles of the double bundle ACL andproviding variable tensioning with a single fixation device, asdescribed herein. The disclosed fixation device would allow each ACLbundle (2 suture tails per bundle) to be variably tensioned independentof the other on a single post.

Although the disclosed fixation device is described for use inperforming single or double bundle ACL reconstruction, it is understoodand within the scope of the present invention for the disclosed fixationdevice to be used in other procedures where tensioning of sutures isdesired.

Variable Tension Posts

FIGS. 1 a through 1 i illustrate one embodiment of a variable tensionpost fixation device. The variable tension post fixation device of FIG.1 a through 1 f includes an outer screw (or sleeve) and an inner keyconfigured to fit within the outer screw (or sleeve). The outer screwand inner key cooperate to provide for variable tension fixation ofsutures, as described below.

In one embodiment of use, a drill guide is placed distal to the exitpoint of the most distal tibial tunnel, and a pilot hole is drilled inthe bone (see FIG. 5). After the pilot hole is drilled, the outer screwof the variable tension post fixation device is placed in the pilothole.

In one embodiment, the outer screw is fully threaded and headless, andincludes a series of concentric channels or bores (t, x, y, z) (FIG. 1a). In one embodiment, the outer screw is inserted nearly flush with thecortex of the bone (FIG. 1 b), and provides a recipient sight for theinner key (see FIGS. 1 d, 1 e). In one embodiment, the inner keyincludes a key tip, a key shaft, and a key head, with the key head beingapproximately the same diameter as the outer screw (FIG. 1 c, 1 d, 1 e).

The concentric bores or channels of the outer screw allow for insertionof the outer screw into the pilot hole in the bone, and locking of theinner key within the outer screw. In one embodiment, the outer screw issecured in the pilot hole with a driver by engaging the driver in thechannel or bore t (FIG. 1 b). After the outer screw is anchored in thebone, the driver is removed and the suture tails are fed through and/orattached to the inner key (FIG. 1 c).

In one embodiment, the key head of the inner key has 2 holes throughwhich sutures are fed. In one embodiment, suture tails 1 and 2 are fedthrough the key head from the bottom up and then tied to each other(FIGS. 1 c, 1 f). This helps to keep the twisted sutures under the keyhead and around the key shaft. In one embodiment, suture tails 3 and 4are fed through a central hole in the key shaft and tied to each other(FIG. 1 c). The key tip is then inserted into the outer screw channel orbore z, and the inner key is rotated in order to tension the sutures(FIG. 1 d). In one embodiment, the inner key is rotated using the samesize driver used for the outer screw. In one embodiment, a collar isprovided around the key head to help prevent the suture tails 1 and 2from slipping onto the driver during rotation of the inner key.

Once the desired tension on the sutures has been obtained, the driver isused to rotate the inner key and advance the key tip through the channelor bore x until the key tip reaches the channel or bore y (FIG. 1 e). Inone embodiment, the sutures are slightly over-tensioned as the key tipis advanced through the channel or bore x and into the locking channelor bore y. Slightly over tensioning the sutures will allow for the innerkey to “unwind” within the locking channel or bore y, as the key tiprotates to the lock position (FIG. 1 a).

In one embodiment, locking pin slots are provided in the key head, andlocking pins are inserted into the slots to prevent the inner key fromrotating relative to the outer screw when the inner key is in the“locked” position (FIGS. 1 e, 1 f). In one embodiment, the locking pinsextend along the key shaft through the key shaft channel or bore x andinto the locking channel or bore y next to the key tip (FIGS. 1 e, 1 a).As such, the key tip of the inner key and, therefore, the inner keyitself is prevented from rotating within the locking channel or bore y.

In one embodiment, if the ACL bundles need to be further tensioned, theentire construct (inner key and outer screw) can be advanced fartherinto the pilot hole by inserting the driver into the key head andturning the entire construct clockwise. Because the outer diameters ofthe outer screw and the inner key are essentially the same, the entireconstruct can be advanced as a unit even beyond the cortex of the tibialbone posteriorly.

The variable tension post fixation device of FIGS. 1 g through 1 i issimilar to the variable tension post fixation device of FIGS. 1 athrough 1 f, however, the inner key of the variable tension postfixation device of FIGS. 1 g through 1 i has a larger diameter head thanthe outer screw (FIG. 1 g, 1 i). The larger diameter head provides moreroom to bring all four suture tails from the bottom up through their ownhole (FIG. 1 h). In one embodiment, suture tails 1 and 2 are fed upthrough the key head and tied to each other, as are suture tails 3 and4. In one embodiment, as described above, a collar is provided aroundthe key head to help keep the sutures from becoming entangled with thedriver. In one embodiment, in addition to the holes for sutures in thekey head, a central hole is provided in the key shaft for additionalsutures (FIG. 1 i).

The inner key of the variable tension post fixation device of FIGS. 1 gthrough 1 i is “locked” in the locking channel or bore y of the outerscrew in a manner similar to that described above. In one embodiment,however, the key head of the inner screw is still spaced or offset fromthe top of the outer screw when the inner key is in the “locked”position (FIG. 1 i). This slight offset allows for further advancementof the entire construct once the inner key is locked to the outer screwwhereby further tensioning of the sutures at the conclusion of theprocedure is possible.

FIGS. 2 a through 2 g illustrate another embodiment of a variabletension post fixation device. In one embodiment, as outlined above, adrill is used to create a pilot hole in the tibia distal to the mostdistal exiting tibial ACL bundle (see FIG. 5). The variable tension postfixation device of FIGS. 2 a through 2 g includes an outer screw and aninner screw. In one embodiment, the outer screw is a fully threadedheadless screw that is inserted flush to the cortex of the tibial bone(FIG. 2 a). In one embodiment, the outer screw is incompletelycannulated and includes side channels that are cut partially along thesides to receive a driver (FIGS. 2 a, 2 b). In one embodiment, thedriver is cylindrical and includes expansion keys or tabs thatcorrespond to the side channels of the outer screw to provide ease ofinsertion and stability when anchoring the outer screw in the bone (FIG.2 c).

In one embodiment, the inner portion of the outer screw of the variabletension post fixation device of FIGS. 2 a through 2 g has threads thatextend to the bottom of the cannulation portion of the screw (FIG. 2 d).In addition, the inner screw is threaded and also partially cannulatedto receive a driver (FIGS. 2 d, 2 e). In one embodiment, the inner screwhas 4 holes formed axially therethrough to accommodate sutures (FIG. 2e). In one embodiment, suture tails 1 and 2 are each fed throughrespective holes in the inner screw and tied to each other, as aresuture tails 3 and 4 (FIG. 2 e). The inner screw is then placed into thethreaded cannulation of the outer screw and advanced with the driveruntil the desired tension is achieved on the sutures (FIG. 2 d).

The variable tension post fixation device of FIGS. 2 f through 2 g issimilar to the variable tension post fixation device of FIGS. 2 athrough 2 e, however, the inner screw of the variable tension postfixation device of FIGS. 2 f through 2 g has a fenestrated end. In oneembodiment, suture tails 1 and 2 are fed through the openings in thefenestrated end and tied to each other, as are suture tails 3 and 4(FIG. 2 f). In one embodiment, a pronged driver is used to engage thefenestrations and advance the inner screw into the outer sleeve toachieve the desired tension on the sutures (FIG. 2 g).

FIGS. 3 a through 3 h illustrate another embodiment of a variabletension post fixation device. In one embodiment, as outlined above, adrill is used to create a pilot hole in the tibia distal to the mostdistal exiting tibial ACL bundle (see FIG. 5). The variable tension postfixation device of FIGS. 3 a through 3 h includes an outer screw and aninner screw. In one embodiment, the outer screw is a fully threadedheaded screw that is inserted flush to the cortex of the tibial bone(FIG. 3 a). In one embodiment, the pilot hole is cored out toaccommodate the head of the outer screw.

In one embodiment, the outer screw is incompletely cannulated andincludes side channels that are cut partially along the sides to receivemating expansion keys or tabs of a cylindrical driver (FIGS. 3 a, 3 b).In one embodiment, external suture eyelets are provided beneath the headof the outer screw such that before completely sinking the outer screwhead flush with the cortex of the tibial bone, suture tails 1 and 2 arefed through the external eyelets and tied to each other (FIG. 3 a, 3 b).The outer screw head is then sunk flush with the cortex of the tibialbone whereby suture tails 1 and 2 are tensioned (FIG. 3 d).

In one embodiment, the shaft of the inner screw includes a central holethrough which suture tails 3 and 4 are fed and then tied to each other(FIG. 3 c, 3 d). In one embodiment, the inner screw includes a partiallythreaded portion that is thread into the outer screw whereby the innerscrew is pressed into the outer screw until the threads of the innerscrew engage the locking threads of the outer screw cannulation (FIG. 3c, 3 d). As such, the inner screw is rotated until the desired tensionis achieved on the suture tails 3 and 4. With the inner screw threadinto the outer screw, the inner screw and the outer screw are now asingle construct. If further tension on the sutures is desired, thedriver may be introduced into the inner screw and the whole constructcan be further rotated and advanced.

In one embodiment, the shaft of the inner screw narrows under the headto accommodate the suture tails 3 and 4 as the inner screw is rotatedwithin the outer screw. In addition, in one embodiment, to avoidentanglement of suture tails 3 and 4 in the locking threads between theinner screw and the outer screw, the sutures are fed through sidechannels provided in the outer screw before the locking threads areengaged.

The variable tension post fixation device of FIGS. 3 e through 3 h issimilar to the variable tension post fixation device of FIGS. 3 athrough 3 d, however, the outer screw of the variable tension postfixation device of FIGS. 3 e through 3 h has a concave outer portion(FIGS. 3 e, 3 g). In addition, the inner screw is free of threads (FIGS.3 f, 3 g).

In one embodiment, suture tails 1 and 2 are fed through the sutureeyelets provided on the outer screw, and the outer screw is thread intothe pilot hole as described above (FIG. 3 g). In addition, sutures tails3 and 4 are fed through the central hole of the shaft of the inner screwand then tied to each other. Thereafter, the inner screw is press fitinto the outer screw to tension suture tails 3 and 4 (FIG. 3 g).

In one embodiment, prior to tensioning suture tails 3 and 4, a cap thatengages the inner screw with its own hex head is placed on the innerscrew. As such, the cap and the inner screw are rotated to achieve thedesired tension on sutures 3 and 4. Once the desired tension isachieved, the inner screw is press fit into the outer screw and the capis crimped onto the outer screw. The outer screw, the inner screw, andthe cap are now a single unit (FIG. 3 h). Thus, further tensioning canbe achieved with the crimping device on the cap by rotating the entireconstruct.

FIGS. 4 a through 4 b illustrate another embodiment of a variabletension post fixation device. In one embodiment, as outlined above, adrill is used to create a pilot hole in the tibia distal to the mostdistal exiting tibial ACL bundle (see FIG. 5). The variable tension postfixation device of FIGS. 4 a through 4 b includes an outer screw and aninner screw. In one embodiment, the outer screw is a fully threadedheaded screw that is inserted flush to the cortex of the tibial bone(FIG. 4 a).

In one embodiment, the outer screw is incompletely cannulated andincludes side channels that are cut partially along the sides to receivemating expansion keys or tabs of a cylindrical driver, as describedabove. In one embodiment, external suture eyelets are provided beneaththe head of the outer screw such that before completely sinking theouter screw head flush with the cortex of the tibial bone, suture tails1 and 2 are fed through the external eyelets and tied to each other(FIG. 4 a). The outer screw head is then sunk flush with the cortex ofthe tibial bone whereby suture tails 1 and 2 are fully tensioned (FIG. 4a).

In one embodiment, the inner screw is free of threads and includes ashaft that fits inside the outer screw (FIG. 4 a). In one embodiment,the head of the inner screw is domed and includes four holes throughwhich suture tails 3 and 4 are fed and then tied together (FIGS. 4 a, 4b). In one embodiment, the head of the inner screw also includes twoadditional holes positioned peripherally which are used to rotate theinner screw and develop the desired tension on suture tails 3 and 4. Inone embodiment, once the desired tension is achieved, two anchoringscrews or pins are inserted through the additional holes in the head ofthe inner screw and into the tibia (FIG. 4 a). The anchoring screws orpins fix the head of the inner screw to the bone and secure the tensionon suture tails 3 and 4.

The embodiments of a variable tension post fixation device describedherein provide orthopaedic surgeons with the option of using a singletibial post for fixation and the ability to provide variable tensionindependently to more than one suture stand.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims.

1. A variable tension post fixation device comprising: an outer screwcomprising a head configured to receive a driver, a conical tip, athreaded shaft extending between the head and the tip, and anincompletely cannulated core; and an inner screw comprising a proximalend, a distal end, and at least one suture hole, wherein the inner screwis configured to be insertably coupled with the outer screw.
 2. Thedevice of claim 1, wherein the outer screw includes at least two sidechannels configured to receive at least two mating expansion tabs of thedriver.
 3. The device of claim 1, wherein the outer screw includes atleast one external eyelet provided on the shaft proximal to the head. 4.The device of claim 1, wherein the incompletely cannulated core is atleast partially threaded.
 5. The device of claim 4, wherein the innerscrew includes a partially threaded portion configured to mate with theat least partially threaded core.
 6. The device of claim 1, wherein theinner screw is configured to mate with the driver independent of theouter screw.
 7. The device of claim 1, wherein an outer diameter of theinner screw is constricted for a length between the proximal end and theat least one suture hole.
 8. The device of claim 1, wherein when theinner screw is assembled with the outer screw, the assembly is rotatablein a unified manner.
 9. The device of claim 2, wherein the at least twoside channels are configured to accommodate sutures extending from aninterior to an exterior of the outer screw.
 10. A device for variabletension suture fixation, comprising: a cylindrical outer screw includinga conical tip, a threaded shaft, a belled head, at least one externaleyelet, and a partially cannulated threaded core; and an elongated innerbody including a central lumen, a threaded head, an opposing tip, and ashaft disposed between the head and the tip, wherein the inner body isconfigured to be removably secured within the partially cannulatedthreaded core, and wherein the inner body cooperates with the outerscrew to provide for variable tension fixation of at least two sutures.11. The device of claim 10, wherein the inner body is configured tosecure and tension a first set of sutures and the outer screw isconfigured to secure and tension a second set of sutures.
 12. The deviceof claim 11, wherein the first set of sutures extend from the centrallumen of the inner body and exit the outer screw through at least oneside channel when fully assembled.
 13. The device of claim 10, whereinthe belled head includes at least one side channel configured to matewith a driver.
 14. The device of claim 10, wherein the threaded head isconfigured to mate with a driver.
 15. The device of claim 10, whereinthe inner body is rotatable within the partially cannulated threadedcore to a locked position.
 16. The device of claim 10, wherein the shaftof the inner body is narrowed for a length between the central lumen andthe threaded head.
 17. A single fixation device for variably tensioningACL bundles, comprising: means for securing and tensioning a pluralityof sutures to allow a first ACL bundle to be variably tensionedindependent of a second ACL bundle.
 18. The device of claim 17, whereinthe means comprises a rotatable outer body, wherein tension of a firstpair of the plurality of sutures is adjusted with rotation of the outerbody.
 19. The device of claim 18, wherein the means further comprises aninner body rotatably coupled within the outer body, wherein a secondpair of the plurality of sutures is independently adjusted throughrotation of the inner body within the outer body.
 20. The device ofclaim 19, wherein the means further comprises the inner body in a lockedposition within the outer body whereby the inner body and the outer bodyare rotated in combination to provide tension to the plurality ofsutures.